Kōshirō Izumi, known as Izzy Izumi in English adaptations, is a central figure in the Digimon Adventure continuity. Orphaned as a baby when his biological parents died in a car accident, he was adopted by distant relatives Izumi Masami and his wife Kae. Witnessing the battle between Greymon and Parrotmon from his Hikarigaoka home in 1995—an event later blamed on terrorism—prompted the family's move to Odaiba. Overhearing his adoptive parents discuss his adoption caused him to subconsciously distance himself, questioning his place as a "true Izumi." Intellectually gifted yet socially reserved, Kōshirō used computers and research as a coping mechanism. Partnered with Tentomon and bearing the Crest of Knowledge, he pursued deep understanding over simple facts. His Digital World journey confronted personal challenges, including an identity crisis. Facing Vademon, he momentarily abandoned his curiosity to save himself and Tentomon, losing his Crest's power. He reclaimed it by embracing his inquisitive nature, enabling Tentomon's evolution to Atlur Kabuterimon. His adoptive parents later revealed his adoption, allowing him to fully accept them and resolve his conflict. His technological expertise proved vital. In Digimon Adventure: Our War Game!, he detected a virus-infected Digitama online and coordinated the fight against Diaboromon. Continuing in Digimon Adventure 02, he supported new Chosen Children and investigated anomalies like the Digimon Kaiser's dark spires. He sacrificed his Crest's power to free the Four Holy Beasts, temporarily limiting Tentomon's evolution, and remained active in later conflicts like Diablomon Strikes Back. In Digimon Adventure tri., attending Tsukishima High School, Kōshirō developed advanced tools like Tai's goggles and a virtual Digimon connection system. His analysis was central to investigating infected Digimon and the Digital World reboot. He demonstrated fluency in French during a conversation with Sora. Intense research focus sometimes led him to neglect his surroundings, causing stress and fatigue. By Digimon Adventure: Last Evolution Kizuna (2010), 21-year-old Kōshirō worked in technology. He played a key role analyzing global coma incidents linked to Eosmon, initially collaborating with Professor Menoa Bellucci. He identified the victims as exclusively Chosen Children and assisted in the digital battle against Eosmon. Unlike Tai and Matt, he lacked a countdown timer on his Digivice, indicating his personal and professional growth remained ongoing. He uncovered critical information about Menoa's past and her connection to the attacks, relaying vital coordinates. Later, by 2027, Kōshirō founded a Digital World research team, collaborating with Kido Shuu and Takenouchi Haruhiko. He married, had a daughter partnered with Motimon, expressed gratitude to Tentomon for helping humanity accept Digimon, and planned to co-author a Digital World encyclopedia. His appearance featured straightened hair with longer bangs, typically wearing professional attire like an olive-green button-up or light blue coat. Kōshirō evolved from a secretive, socially anxious child into a confident adult balancing intellect with emotional connections. His foundational relationship with Tentomon symbolized mutual growth and acceptance.